Prostate Cancer Disparities Greatest in Low-Risk Disease

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Black men in the United States are known to suffer disproportionately from prostate cancer. Now, a new study investigating prostate cancer deaths by race has found that African-American men have twice the chance of dying from low-risk prostate cancer than men of other racial and ethnic groups, even after adjusting for socioeconomic status.

The study, led by UC San Francisco, raises intriguing questions about whether the biology of low-risk prostate cancer in black men is distinct from that of other ethnicities.

The research appears in JAMA, the Journal of the American Medical Association.

“This study suggests we need more research on the factors that may make low-risk prostate cancer more deadly in black men,” said Franklin W. Huang, MD, PhD, a UCSF assistant professor of medicine whose research uses cancer genomics and centers on prostate cancer in African-American men and underserved cancer patients. Huang’s laboratory research focuses on identifying the biological features of tumors that drive cancer disparities.

African-American men have a 15 percent chance of developing prostate cancer, compared to 10 percent for white men, according to the National Cancer Institute. In addition, the risk of dying from prostate cancer for African-American men is about 4 percent compared to about 2 percent for white men.

The new study investigated prostate cancer mortality by race and by Gleason score, the latter of which is considered the best independent predictor of prostate cancer outcomes. A Gleason score of 6 indicates low-grade disease and a Gleason score of 7 to 10 indicates intermediate- to high-grade disease. The researchers analyzed data from Surveillance, Epidemiology and End Results (SEER) at two points: 36 months after prostate cancer diagnosis (192,224 men) and 65 months after diagnosis (403,022 men).

They found that for both timeframes, black patients with prostate cancer were younger than nonblack patients (62 years old on median compared to 65), and those with Gleason 6 disease had a higher risk of prostate cancer death compared with nonblack patients. Black men with Gleason 6 prostate cancer had a two-fold increased risk of dying from prostate cancer compared to men from other racial/ethnic groups.

“We may be underestimating the risk that African-American men with low-risk face as racial disparities were greatest in low-grade (Gleason 6) disease compared to higher-risk (Gleason 7 to 10) disease,” said Huang. “The data we used allowed us to control for socioeconomic and treatment selection differences, and support our hypothesis that low-grade prostate cancer may be distinct in black men.

“Still, other potential contributors to the disparity could include racial differences in patient characteristics and the patterns of care that the men receive,” Huang said.

UCSF is one of four National Cancer Institute cancer centers in the U.S. conducting a study of some 10,000 African-American men with prostate cancer through the $26.5 million project known as Research on Prostate Cancer in Men of African Ancestry: Defining the Roles of Genetics, Tumor Markers, and Social Stress, or RESPOND. Researchers will investigate environmental and genetic factors linked to the aggressiveness of prostate cancer in black men to better understand why environmental and genetic factors can lead to prostate cancer that grows and spreads quickly. Huang is co-leading the tumor genetics part of the study. UCSF professor Scarlett Gomez, PhD, of the department of epidemiology and biostatistics, is leading a major part of the study on social stressors and aggressive prostate cancer in African-American men.

Authors: The JAMA paper’s first author is Brandon A. Mahal, MD, of the Harvard Radiation Oncology Program in Boston Mass.; other authors are Rebecca A. Berman, MD, associate professor of medicine and director of UCSF’s Internal Medicine Residency Program; and Mary-Ellen Taplin, MD, of the Dana-Farber Cancer Institute in Boston.

Funding: Mahal is funded by the Prostate Cancer Foundation-American Society for Radiation Oncology Award to End Prostate Cancer. Huang is funded by the Prostate Cancer Foundation Young Investigator Award and the Department of Defense Prostate Cancer Research Program. Taplin is funded by the Prostate Cancer Foundation challenge grant 6296701.

Disclosures: None reported.

This article was originally published on December 18, 2018, by the University of California, San Francisco, News Center. It is republished with permission.